3상 혼합조직 구상흑연주철의 (球狀黑鉛鑄鐵) 강인화에 미치는 특수열처리의 영향에 관한 연구

최현수,김석원 ( Hyun Soo Choi,Sug Won Kim ) 한국주조공학회 1989 한국주조공학회지 Vol.9 No.6

N/A This study is aimed to investigate the effect of cyclic heat treatment which is special heat treatment on the strength and toughness in Multi-phase(Ferrite-Bainite-Martensite) Ductile cast irons. Spceimens were austenitized at eutectoid transformation temperature range(α+γ) for 30min and austempered at 300℃ and 400℃ for different holding times, and then quenched in ice water to obtain the multi-phase(Ferrite-Bainite-Martensite) structure from various prior structures, which was obtained by various cyclic heat treatments. As the number of cycle in cyclic heat treatment increased, volume fraction of pearlite increased and the its morphology was refined. As the number of cycle in cyclic heat treatment increased, the multi-phase(Ferrite-Bainite-Martensite) was dispersed in whole matrix as refined island phase. Particularly, martensite among the multi-phase gradually became a spherical shape. Good combination in impact energy and tensile strength was detained in 840℃-300℃-15min condition after 10 cycles in cyclic heat treatment, and its multi-phase volume fraction is Ferrite(50%)-Martensite(13%)-Bainite(37%).

저수지 붕괴 시 홍수 분석에 관한 연구 동향

최현수,Choi, Hyun-Soo 한국관개배수위원회 2009 한국관개배수논문집 Vol.16 No.1

생체유리 및 천연산호 이식재가 성견 치조골 결손부의 재생에 미치는 영향

최현수,이만섭,박준봉,허익,권영혁,Choi, Hyun-Soo,Lee, Man-Sup,Park, Joon-Bong,Herr, Yeek,Kwon, Young-Hyuk 대한치주과학회 1996 Journal of Periodontal & Implant Science Vol.26 No.4

The purpose of this study was to study of the effects of the bioglass and the natural coral on healing process of the alveolar bone defects. Three adult dogs aged 1 to 2 years were used in this study. Experimental alveolar bone defects were created surgically with surgical bur and bone chisel at the furcation area of the buccal surface of the right and left mandibular 3rd, 4th premolars. Twelve experimental alveolar bone defects were devided into four groups according to the type of graft materials. The groups were as follows : 1. flap operation with root planing & curettage(Negative control group) 2. flap operation with autogenous bone(Positive control group) 3. flap operation with bioglass(BG group) 4. flap operation with natural coral(NC group) At 2, 4, and 8 weeks, the dogs were serially sacrificed and specimens were prepared with Hematoxylin-Eosin stain for light microscopic evaluation. The results of this study were as follows : 1. The defect areas were filled with granulation tissue at two weeks in negative control group. But in other groups, the appearance of connective tissues around graft materials were formed more densely and the response of inflammation by graft materials itself was not found. 2. In every control and experimental groups at two weeks, there was seen the accumulation of the formation of new bone trabeculae at the bottom of defects and gradually expanded toward the graft materials and in autogenous group there was slightly seen the formation of new cementum. 3. There was seen the erosion of central portion of bioglass particles at two weeks in BG group, and the erosion of the central portion was developed more progressively and was filled with bone-like tissues at eight weeks. 4. The natural coral particles were encapsulated by densely connective tissues and seen the formation of new bone tissues at four weeks and developed more new bone and cementum formation at eight weeks. From the results of this study, the bioglass and the natural coral may be biocompatible and have a weak adverse reaction to the periodontal tissues.

선행 제왕절개 후의 질식 분만시 성공군과 실패군의 비교연구

최현수(Hyun Soo Choi),이상욱(Sang Wook Yi),오영승(Young Seung Oh),진규섭(Kyu seop Jin),이보연(Bo yon Lee),이선경(Seun Kyung Lee),허주엽(Chu Yeop Huh),김승보(Seung Bo Kim) 대한산부인과학회 1999 Obstetrics & Gynecology Science Vol.42 No.10

Objectives: Vaginal birth or trial of labor after previous cesarean section has become one of the most remarkable changes in obstetric practice. The safety and efficacy of a trial of labor and vaginal birth after previous cesarean are well documented. The purpose of this report is to predict the likelihood of vaginal birth in patients undergoing a trial of labor after previous cesarean delivery using factors known at the time of hospital admission. Method: In this retrospective study, 120 women who attempted vaginal birth at Kyung-Hee University Hospital from March 1997 to March 1999. An attempt to identify possible prognostic factors for success of such a trial was made and we evaluated the variables of significant predictive value and the patients' characteristics in the success group and failure group of women who attempted VBAC. Result: 87 cases(72.5%) in 120 cases succeeded in VBAC and 33 cases(27.5%) failed. In this comparative groups in VBAC, there was significant difference in CPD index(cephalopelvic disproportion index) and Bishop score, but no significant difference in gestational age, the estimated fetal weight by sonography and newborn birth weight. Conclusion: In this study, Bishop score and CPD index and age may be useful and valid predictor of success in VBAC and this information could be particularly valuable. The CPD index may prove most important in determining if a vaginal birth should occur after a cesarean section because it can clearly identify some patients who need a repeat cesarean section.

불균형 데이터 분류를 위한 과다 추출 기법의 검증

최현수(Hyun-soo Choi),윤성로(Sungroh Yoon) 한국정보과학회 2015 한국정보과학회 학술발표논문집 Vol.2015 No.6

Taxol-Cisplatin 화학 요법에 실패한 말기 난소암 환자에서 Topotecan으로 완전 관해된 1예

최현수(Hyun Soo Choi),허주엽(Chu Yeop Huh),김승보(Seung Bo Kim) 대한산부인과학회 2000 Obstetrics & Gynecology Science Vol.43 No.5

Ovarian cancer has the highest mortality rate among gynecologic malignancies in developed countries. Most women present with advanced disease and require a combination of surgery and chemotherapy. One patient presented with recurrent ovarian cancer was initially treated with taxol and platinum-based compounds. Although response to these agents occurred, tumor progression was evident by elevated CA 125 levels and CT findings after a period of 4 months. This patient was then treated with topotecan and exhibited a response and stopped therapy. Topotecan exhibited activity in this patient with ovarian cancer resistent to both platinum and paclitaxel. We report a case of advanced ovarian cancer which was treated with topotecan after taxol-cisplatin treatment failed.

자기진단 CPGFRP의 파괴예측기능 평가를 위한 콘크리트 적용실험

최현수 ( Hyun Soo Choi ),박진섭 ( Jin Sub Park ),정민수 ( Min Soo Jnng ),강병희 ( Byeung Hee Kang ) 한국건축시공학회 2003 한국건축시공학회 학술발표대회 논문집 Vol.3 No.2

To maintain serviceability of concrete structure more than proper it is necessary not only predict service life through periodical monitor but also need monitoring system to recognize optimal time and method for repair. Recently, CPGFRP, replacing some GFRP with CF, is developed and used for monitoring concrete fraction. But dramatic resistance change of CPGFRP is showed below 0.5% strain and it is not small strain in terms of monitoring micro crack in concrete. In other word, monitoring with CF is not suitable in low stress but hight stress. In this study, we accessed applicable possibility and reliability of CPGFRP composite as monitoring sense that is proved very sensitive to stress through domestic and oversea previous study. CPGFRP composite plays a role in specimen like steel and increases flexural strength. CPGFRP composite shows resistance increasement in micro crack. In particular, CPGFRP is more sensitive than strangage in low stress. Resistance change ratio curve is very similar to strain curve so sensitivity and reliability is very excellent to monitor concrete fracture.

세라믹 열교환기의 성능평가를 위한 실험적 연구

최현수(Hyun Soo Choi),신동훈(Donghoon Shin) 한국연소학회 2011 한국연소학회지 Vol.16 No.1

Exhaust gas of an industrial furnace used at such as metallurgy or ceramic manufacturing usually contains thermal energy with high temperature which can be recycled by heat exchanger. However, when the temperature of the exhaust gas is high such as more than 1,000℃, ordinary metallic heat exchanger cannot fully recover the heat due to the limitation of operating temperature depending on the material property. In the present study, a compact ceramic heat exchanger of cross flow type is introduced and evaluated by heat exchange rate and operating temperature. The ceramic heat exchanger can endure the gas temperature more than 1,300℃, and its volumetric heat exchanging rate exceeds 1 ㎿/㎥. The experimental data is also compared with the previous numerical result which shows reasonable agreement. Meanwhile, the gas leakage rate is measured to be about 3~4%, and heat loss to environmental air is about 23~26% of the fuel energy.

경제위기(經濟危機) 이후(以後) 도시근로자가구(都市勤勞者家口)의 빈곤역동성(貧困逆動性) 및 빈곤기간(貧困期間) 연구(硏究)

최현수 ( Hyun-soo Choi ) 한국보건사회연구원 2002 保健社會硏究 Vol.22 No.1

This study analyzes empirically the poverty dynamics and the poverty duration of the working poor. For the purpose of the analysis, the study composed the 10 quarters panel data of urban worker households, with the reference to the Household Income and Expenditure Survey from the first quarter of 1998(just after the economic crisis) to the second quarter of 2000(just before the Minimum Standard Living Guarantee System). From the results of analysis, this study draws the following implications: First, the poverty dynamics index, which was about 5~ 6% at the economic crisis, went down to 3~4% after the second quarter of 1999. This shows that the poverty dynamics became stable in the process of overcoming the economic crisis. Second, Two-thirds of households, which once had experienced poverty, stayed in poverty transiently for only one quarter. On the other hand, only about 10 percent of households have stayed in poverty for more than four quarters. Third, the longer the poverty duration is, the lower the probability of escaping from poverty. This means if low-income families failed to escape from poverty in its early stage, it would be increasingly difficult for them to get out of poverty. Lastly, the characteristics of the short-term poor households are similar to those of the non-poor households in many respects.

DAMBRK 모형에 의한 댐 하류지역의 홍수분석

최현수(Hyun Soo Choi)(崔賢洙),맹승진(Seung Jin Maeng)(孟昇辰),김병준(Byeoung Jun Kim)(金炳俊) 위기관리 이론과 실천 2011 Crisisonomy Vol.7 No.1

본 연구에서는 저수지가 붕괴된 것으로 가정하에 DAMBRK 모형을 사용하여 저수지 하류지역 하도의 홍수량에 따른 수리학적 거동 분석을 실시하였다. 저수지 상류에서 유입되는 PMF와 댐 붕괴홍수량을 추정한 결과, 상류에서 유입되는 홍수량은 강우 지속시간 6시간에서 1,281㎥/s, 댐의 붕괴로 인한 대표홍수량은 붕괴조건 2Hd-0.4시간에서 2,846㎥/s로 추정되었다. 이러한 조건을 바탕으로 저수지 붕괴모의를 실시하여 하류지역의 홍수파 영향분석 결과 저수지로부터 하류 3.2㎞ 지점의 최초 홍수파 도달시간은 약 24분, 6.0㎞ 지점은 약 1시간 정도가 소요되는 것으로 분석되었다. 저수지 붕괴유출수문곡선 산정을 위해 붕괴지속시간은 0.1∼0.5시간, 댐높이는 1Hd∼3Hd 범위로 하여 총 15개 조건별로 붕괴홍수량을 산정하였다. 저수지의 붕괴방류 조건별 홍수량 중에서 최소의 홍수량이 산정된 1Hd-0.5시간과 최대 홍수량이 산정된 3Hd-0.1시간에 따른 저수지 하류의 홍수 분석 결과, 저수지로부터 하류부로 갈수록 홍수량과 홍수위의 증가가 둔화되었다. 이러한 현상은 지형의 경사도 완화, 평야지 전개에 따른 통수단면 확대 및 중류지역에서의 저류효과 등에 기인하는 것으로 판단된다. 본 연구에서 댐의 높이는 최고점과 최저점(최고값)을 기준으로 적용하였다. 그러나 실제 댐의 높이는 지점에 따라 다르며, 실제 붕괴가 발생한다 해도 댐의 어느 지점에서 발생할 지는 정확하게 예측할 수 없다. 그러므로 댐 평균 높이의 관점으로 볼 때 붕괴유출수문곡선은 15개의 붕괴모의 조건 중에서 붕괴단면의 높이가 댐 높이의 3분의 1 값으로 적게 나타나는 붕괴평균폭(Bm)-1Hd 조건은 배제하고, 붕괴단면의 높이가 댐 높이의 3분의 2 이상의 값을 나타내는 붕괴평균폭(Bm)-2Hd, 3Hd조건 범위 내에서 적용하는 것이 적정한 것으로 판단되었다. In this study, the inundation in the downstream area of the reservoir based on the assumption of the destruction of a reservoir as a representative hydraulic structure was analyzed using the DAMBRK model. With the assumption that PMF and the flood discharge resulting from a dam breach flow in from the reservoir upstream, the flood discharge flowing in from upstream was estimated to reach 1,281㎥/s for the 6 hours duration of rainfall and the maximum flood discharge resulting from the dam breach was 2,846㎥/s under breach conditions, which was 2Hd-0.4 hr. Based on these conditions, a simulation of reservoir failure was conducted in this study. In the analysis of the degree of influence of the flood on the downstream area, the time that took the first flood to reach the downstream area located 3.2 ㎞ from the reservoir was 24 min, and approximately 1 hour for that located 6.0 ㎞ from the reservoir. For the estimation of the reservoir failure outflow hydrograph, the breach flood discharge was estimated under 15 conditions, with 0.1-0.5 hr breach duration variation and within dam height scope of 1∼3Hd. As a result of this estimation, the maximum flood discharge was within the 3Hd-0.1 hr range and the minimum was within the 1Hd-0.5 hr range. The analysis of the flood in the downstream area of a reservoir revealed that from the reservoir to the downstream area, the increase in the flood discharge and level was reduced. It can thus be concluded that this result is due to the ease of geographic gratitude, the water-containing section expansion in accordance with the development of the plain and the pooling effect in midstream regions. In this research, the height of the dam, ranging from maximum to minimum, was applied. The height of the dam, however, differs at various points, and where a breach will occur in the whole dam cannot be precisely determined. Therefore, from the viewpoint of the mean height of a dam, under the aforementioned 15 conditions, it is reasonable to exclude the conditions of the mean width of the breach (Bm)-1Hd which the height of the dam breach section appears to be below one-third, and to apply the conditions of mean width of the breach (Bm)-2Hd, 3Hd which the height of the dam breach section appears to be above two-thirds.